Dehydrogenation of alkyl aromatic compound over a gallium-zinc catalyst

Abstract

A process for the dehydrogenation of an alkyl aromatic compound, preferably ethylbenzene, to a vinyl aromatic compound, preferably styrene, involving dehydrogenating the alkyl aromatic compound over a catalyst containing gallium, zinc, optionally alkali or alkaline earth, optionally manganese, and optionally a noble metal, deposited on a catalyst support, preferably, a transitional alumina. Optionally, the dehydrogenation feedstream may contain an alkane, preferably ethane, which is simultaneously dehydrogenated to an alkene, preferably ethylene. The dehydrogenation process can be integrated into a process of producing a vinyl aromatic compound, such as styrene, from a raw material base comprised of an alkane and an aromatic compound, such as, ethane and benzene.

1 . A process of preparing a vinyl aromatic compound comprising contacting a dehydrogenation feedstream comprising an alkyl aromatic compound and optionally a diluent with a dehydrogenation catalyst under reaction conditions sufficient to prepare a dehydrogenation product stream comprising a vinyl aromatic compound; the catalyst comprising gallium and zinc deposited on a catalyst support.  
     
     
         2 . The process of  claim 1  wherein the alkyl aromatic compound is a C 8-30  alkyl aromatic compound.  
     
     
         3 . The process of  claim 1  wherein the alkyl aromatic compound is selected from ethylbenzene, ethyltoluene, ethylxylene, diethylbenzene, isopropylbenzene, and mixtures thereof.  
     
     
         4 . The process of  claim 1  wherein gallium is loaded on the catalyst support in an amount greater than about 0.1 and less than about 10 weight percent, calculated as is gallium oxide and based on the total weight of the catalyst composition.  
     
     
         5 . The process of  claim 1  wherein zinc is loaded on the catalyst support in an amount greater than about 0.01 and less than about 8 weight percent, calculated as zinc oxide and based on the total weight of the catalyst composition.  
     
     
         6 . The process of  claim 1  wherein the catalyst support is selected from alumina, silica, silica-alumina, aluminosilicates, titania, zirconia, and mixtures thereof.  
     
     
         7 . The process of  claim 6  wherein the catalyst support comprises a transitional alumina.  
     
     
         8 . The process of  claim 1  wherein the catalyst further comprises a promoter selected from elements of Group IA, Group IIA, and combinations thereof.  
     
     
         9 . The process of  claim 8  wherein the loading of promoter is greater than about 0.01 and less than about 5 weight percent, calculated as promoter metal oxide and based on the total weight of the catalyst composition.  
     
     
         10 . The process of  claim 1  wherein the catalyst further comprises manganese in a concentration from greater than about 0.01 to less than about 3 weight percent, calculated as elemental manganese and based on the total weight of the catalyst composition.  
     
     
         11 . The process of  claim 1  wherein the catalyst further comprises from greater than 1 ppm to less than about 100 ppm platinum group metal.  
     
     
         12 . The process of  claim 1  wherein the catalyst has a surface area of greater than about 20 m 2 /g and less than about 280 m 2 /g, and optionally, an average particle diameter of greater than about 5 microns and less about 500 microns.  
     
     
         13 . The process of  claim 1  wherein the catalyst composition is prepared by first depositing zinc onto the support and thereafter depositing gallium and optionally a Group IA or Group IIA element, a platinum group metal, manganese, or a mixture thereof onto the support.  
     
     
         14 . The process of  claim 1  wherein the temperature ranges from greater than about 400° C. to less than about 750° C.  
     
     
         15 . The process of  claim 1  wherein the pressure ranges from greater than about 1 psia (6.9 kPa) to less than about 73 psia (503.3 kPa).  
     
     
         16 . The process of  claim 1  wherein a diluent is used, and the diluent is selected from nitrogen, argon, helium, methane, carbon dioxide, and mixtures thereof.  
     
     
         17 . The process of  claim 1  wherein the process is conducted in a fluidized bed reactor.  
     
     
         18 . The process of  claim 1  wherein the dehydrogenation reaction is conducted in the absence of co-fed oxygen or similar oxidant and/or steam.  
     
     
         19 . The process of  claim 1  wherein the catalyst is transported to a regenerator for regeneration under air or oxygen at a temperature greater than about 400° C. and less than about 850° C.  
     
     
         20 . The process of  claim 1  wherein the vinyl aromatic compound comprises styrene, vinyltoluene, vinylxylene, t-butylstyrene, αmethylstyrene, divinylbenzene, or a mixture thereof.  
     
     
         21 . The process of  claim 1  wherein the dehydrogenation feedstream comprises an alkane, and the dehydrogenation product stream comprises an alkene.  
     
     
         22 . The process of  claim 1  wherein the dehydrogenation feedstream comprises ethylbenzene and ethane, and the dehydrogenation product stream comprises styrene and ethylene.  
     
     
         23 . An integrated process of preparing a vinyl aromatic compound comprising (a) dehydrogenating an alkane in the presence of a first dehydrogenation catalyst under reaction conditions sufficient to prepare an alkene; (b) contacting the alkene with an aromatic compound in the presence of an alkylation catalyst under reaction conditions sufficient to prepare an alkyl aromatic compound; and (c) dehydrogenating the alkyl aromatic compound with a second dehydrogenation catalyst under reaction conditions is sufficient to prepare a vinyl aromatic compound; the catalyst for step (c) comprising gallium and zinc deposited on a catalyst support.  
     
     
         24 . The process of  claim 23  wherein the alkane is ethane; the alkene is ethylene; the aromatic compound is benzene; the alkyl aromatic compound is ethylbenzene; and the vinyl aromatic compound is styrene.  
     
     
         25 . The process of  claim 23  wherein the catalyst further comprises one or more elements selected from the group consisting of Group IA, Group IIA, manganese, and platinum group metals.  
     
     
         26 . The process of  claim 23  wherein the alkane dehydrogenation step (a) occurs simultaneously in the same reactor and with the same gallium-zinc catalyst as the alkyl aromatic dehydrogenation step (c).  
     
     
         27 . The process of  claim 23  wherein the catalyst support is a transitional alumina.  
     
     
         28 . The process of  claim 23  wherein the catalyst is prepared by first depositing zinc onto the support and thereafter depositing gallium and optionally a Group IA or Group IIA element, a platinum group metal, manganese, or a mixture thereof onto the support.  
     
     
         29 . A catalyst composition comprising gallium and zinc, optionally manganese, optionally a platinum group metal, and optionally one or more Group IA or IIA metals, deposited on a transitional alumina support.  
     
     
         30 . The catalyst composition of  claim 29  wherein the catalyst is prepared by first depositing zinc onto the support and thereafter depositing gallium and any other optional elements onto the support.